Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$60.62	11.769%	$67.7544	$67.75	$67.75	$67.80
Purchase #2	$205.59	7.724%	$221.4698	$221.47	$221.45	$221.50
Purchase #3	$33.89	4.413%	$35.3856	$35.39	$35.40	$35.40
Purchase #4	$105.89	8.208%	$114.5815	$114.58	$114.60	$114.60
Purchase #5	$212.56	8.105%	$229.788	$229.79	$229.80	$229.80
Purchase #6	$37.61	10.586%	$41.5914	$41.59	$41.60	$41.60
Purchase #7	$85.82	7.253%	$92.0445	$92.04	$92.05	$92.00
7 purchase totals =	$741.98		$802.6152	$802.61	$802.65	$802.70